1. Field
Aspects of these disclosures relate to a positive electrode for a rechargeable lithium ion battery and a rechargeable lithium ion battery including the same.
2. Description of the Related Art
Recently, because a rechargeable lithium ion battery that can be used for a mobile phone, a laptop computer, or the like has been required to be of much higher capacity, there has been an attempt to obtain high-capacity and high energy density by setting a high charge, which results in an improved utilization ratio of the positive electrode.
For example, when a lithium manganese-based oxide such as LiMn2O4 or the like is used as a positive active material, it may be deposited into manganese metal by an insertion reaction of lithium ions accompanied by charge and discharge. However, when the manganese metal is deposited and accumulated in a negative electrode, the rechargeable lithium ion battery may exhibit deteriorated cycle characteristics due to destruction of the separator or degradation of the negative electrode.
That is, when a metal is eluted from the positive active material, the metal may be deposited on the negative electrode or oxidize the separator, thus degrading the rechargeable lithium ion battery. Since this elution of transition elements may become severe at a high voltage and a high temperature, it may bring about severe deterioration of a positive electrode at a high voltage and a high temperature. This deterioration may increase impedance (resistance) of a rechargeable lithium ion battery, causing its cycle characteristics to deteriorate.
In order to solve this problem, a method of suppressing degradation of an electrolyte solution, a negative electrode, or a separator by interposing an aramid resin (wholly aromatic polyamide resin) layer between a positive electrode and the separator has been suggested. However, this method cannot suppress a metal from being eluted from portions of the positive active material inside the positive electrode where those portions are not in contact with the aramid resin layer.